1. Field of the Invention
The present invention relates generally to a core for a gliding board and, more particularly, to a core for a snowboard.
2. Description of the Art
Specially configured boards for gliding along a terrain are known, such as snowboards, snow skis, water skis, wake boards, surf boards and the like. For purposes of this patent, "gliding board" will refer generally to any of the foregoing boards as well as to other board-type devices which allow a rider to traverse a surface. For ease of understanding, however, and without limiting the scope of the invention, the inventive core for a gliding board to which this patent is addressed is disclosed below particularly in connection with a core for a snowboard.
A snowboard includes a tip, a tail, and opposed heel and toe edges. The orientation of the edges depends upon whether the rider has her left foot forward (regular) or right foot forward (goofy). A width of the board typically tapers inwardly from both the tip and tail towards the central region of the board, facilitating turn initiation and exit, and edge grip. The snowboard is constructed from several components including a core, top and bottom reinforcing layers that sandwich the core, a top cosmetic layer and a bottom gliding surface that typically is formed from a sintered or extruded plastic. The reinforcing layers may overlap the edge of the core and, or alternatively, a sidewall may be provided to protect and seal the core from the environment. Metal edges (not shown) may wrap around a partial, or preferably a full, perimeter of the board, providing a hard gripping edge for board control on snow and ice. Damping material to reduce chatter and vibrations also may be incorporated into the board. The board may have a symmetric or asymmetric shape and may have either a flat base or, instead, be provided with a slight camber.
A core may be constructed of a foam material, but frequently is formed from a vertical or horizontal laminate of wood strips. Wood is an anisotropic material; that is, wood exhibits different mechanical properties in different directions. For example, the tensile strength, compressive strength and stiffness of wood have a maximum value when measured along the grain direction of the wood, while the mutually orthogonal directions perpendicular to the grain have a minimum value for these properties. In contrast, an isotropic material exhibits the same mechanical property regardless of its orientation.
Wood cores have traditionally been constructed with the grain 20 of all of the wood segments running either parallel to the base plane of the core (tip-to-tail), also known as "long grain" (FIGS. 1-2), perpendicular to the base plane, also known as "end grain" (FIGS. 3-4), or in a mixture of long grains and end grains where strips of the two types of grains are successively alternated. It also has been known to orient the long grain transversely across the core, in an edge-to-edge relationship. Consequently, in known wood cores, the segments have been oriented so that the grain extends in parallel to at least one of the orthogonal axes of the core. To date, however, the mechanical properties of the wood segments have been sufficient in both axial and off-axis directions to respond to the various directional forces applied to the board.
Snowboard manufacturers continually strive to produce a lighter board. It is known to reduce the weight of a board by employing lighter density materials in the core. As the density of wood decreases, however, mechanical properties may also decrease. A lower density wood segment that is oriented in standard fashion, with a long grain running tip-to-tail or edge-to-edge or an end grain extending perpendicular to the core, may be insufficient to withstand the loads commonly applied to a board during riding. Accordingly, there is a demand for an arrangement of a lightweight core for a gliding board that is capable of carrying various on and off-axis force induced stresses.
Dynamic loading conditions encountered during riding induce various bending and twisting forces on the board. The core and reinforcing layers are the structural backbone of the board, cooperating together to withstand these shear, compressive, tensile and torsional stresses. These force induced stresses may not be applied uniformly across the board but, rather, localized regions may be subject to a greater magnitude of a particular force. However, the core may not be specifically tuned to carry these localized loads.
For example, a rider usually lands a jump on the tail end, so it is that region of the board that typically encounters significant bending loads resulting in high longitudinal shear stresses. When a rider executes a hard turn on edge, the board typically is subjected to significant transverse bending loads resulting in high transverse shear stresses in the region between the edge and centerline of the board. Because bindings are mounted in an intermediate region of the board, significant compression strength may be required to withstand high compression loads applied by the rider to this region when landing a jump or during a hard turn on edge. Further, forces exerted on the bindings may create high point loads that can lead to pull out of the binding insert fasteners. The region of the board between the rider's feet may encounter significant torsional loads due to opposing board twist along the board centerline when initiating or exiting a turn.
Accordingly, it would be advantageous to provide a core for a gliding board that is tuned to one or more specific, localized stresses or to a combination of such localized stresses.